EP0534358B1 - Méthode pour la production d'un produit moulé de mousse de polyuréthane à peau intégrale - Google Patents

Méthode pour la production d'un produit moulé de mousse de polyuréthane à peau intégrale Download PDF

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Publication number
EP0534358B1
EP0534358B1 EP92116164A EP92116164A EP0534358B1 EP 0534358 B1 EP0534358 B1 EP 0534358B1 EP 92116164 A EP92116164 A EP 92116164A EP 92116164 A EP92116164 A EP 92116164A EP 0534358 B1 EP0534358 B1 EP 0534358B1
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EP
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Prior art keywords
reacting mixture
mold
cavity
polyurethane foam
mixture
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP92116164A
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German (de)
English (en)
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EP0534358A1 (fr
Inventor
Akira c/o TOYODA GOSEI Technical Center Mabuchi
Osamu c/o TOYODA GOSEI Tech. Center Yamanaka
Naoyuki c/o TOYODA GOSEI Tech. Center Kumagai
Satoru c/o TOYODA GOSEI Tech. Center Ono
Motoshi c/o TOYODA GOSEI Tech. Center Matsuura
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Toyoda Gosei Co Ltd
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Toyoda Gosei Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/58—Moulds
    • B29C44/588—Moulds with means for venting, e.g. releasing foaming gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/3402—Details of processes or apparatus for reducing environmental damage or for working-up compositions comprising inert blowing agents or biodegradable components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/60—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S425/00—Plastic article or earthenware shaping or treating: apparatus
    • Y10S425/812—Venting

Definitions

  • the present invention relates to a method for producing an integral skin polyurethane foam having a non-porous, solid layer on its surface.
  • the method is suitable for the production of polyurethane foams by so-called reaction injection molding (RIM hereinafter).
  • RIM reaction injection molding
  • Examples of the polyurethane foams include automotive parts such as steering wheels, steering wheel pads, instrument panels, console box lids, glove box lids, headrests, armrests, and air spoilers.
  • polyurethane foams is an integral skin semi-rigid polyurethane foam. It is produced in the following manner from a long-chain polyol having a molecular weight of the order of thousands, a low-molecular polyol having a molecular weight of the order of tens to hundreds, a catalyst, a pigment, a blowing agent (trichlorofluoromethane or freon-11 or simply freon hereinafter), and an isocyanate. All the components except isocyanate are preliminarily mixed to give a polyol mixture. The polyol mixture is mixed with the isocyanate by a mixing head in a prescribed ratio to give a reacting mixture. Finally, the reacting mixture is injected into a mold cavity made of a highly heat-conductive material, so that it expands in the mold cavity.
  • the polyol mixture and isocyanate Upon injection into the mold cavity, the polyol mixture and isocyanate undergo the urethane-forming reaction, which is exothermic enough to vaporize the fleon in the reacting mixture into a myriad of bubbles.
  • the reacting mixture slowly expands and flows in the mold cavity, expelling the air from the vent hole of the mold cavity when it has reached the vent hole.
  • the urethane-forming reaction and the vaporization of freon take place simultaneously, sustaining a myriad of freon bubbles.
  • the consequence of the reaction is the formation of a highly expanded core at the center of the mold cavity.
  • the reacting mixture close to the walls of the mold cavity undergoes the urethane-forming reaction more slowly than that at the center because the reaction heat dissipates through the walls of the mold cavity The slower the reaction, the less the reaction heat. This suppresses the vaporization of freon and hence generates a less number of freon bubbles. Freon bubbles are compressed or collapsed by the internal foaming pressure.
  • the EP-A-0 006 381 discloses a process for producing a polyurethane foam which comprises feeding a reaction mold with polyurethane polymerization precursors, then plugging the mold, and then evacuating the mold for expanding the reaction mixture in the evacuated mold cavity without any troublesome blowing agent like freon.
  • the present invention was completed to solve the above-mentioned problems. It is an object of the present invention to provide a new method for producing an integral skin polyurethane foam efficiently with a minimum of loss of the reacting mixture, without using troublesome freon or any other blowing agent, said integral skin polyurethane foam having a better appearance and feel and better physical properties than those which are produced by using freon.
  • the process for producing an integral skin polyurethane foam according to claim 1 is provided.
  • the apparatus for producing an integral skin polyurethane foam comprises a mold having a cavity and a vent, a vacuum chamber communicating with the cavity through the vent, a vacuum pump to evacuate the cavity through the vacuum chamber, and a sight glass attached to the vacuum chamber so as to make the vicinity of the vent visible from the outside of the vacuum chamber.
  • Fig. 1 is a half sectional view showing the vacuum chamber and mold (in the open position) used in the first example of the present invention.
  • Fig. 2 is a half sectional view showing RIM operation under way, with the mold closed, in the apparatus as shown in Fig. 1.
  • Fig. 3 is a sectional view taken along line III-III of Fig. 2.
  • Fig. 4 is a partly enlarged sectional view showing a steering wheel pad produced by the apparatus shown in Fig. 1.
  • Fig. 5 is a schematic diagram showing the mixing unit for the reacting mixture.
  • Fig. 6 is a sectional view showing the vacuum chamber and mold (in the open position) used in the second example of the present invention.
  • Fig. 7 is a plan view showing the lower casing of the vacuum chamber and the movable half of the mold (in the open position) in the apparatus as shown in Fig. 6.
  • Fig. 8 is a sectional view showing RIM operation under way, with the mold closed, in the apparatus as shown in Fig. 6.
  • Fig. 9 is a side view showing RIM operation under way, with the mold closed, in the apparatus as shown in Fig. 6.
  • Fig. 10 is a sectional view of the sight glass in the apparatus as shown in Fig. 6.
  • Fig. 11 is a sectional view of the apparatus as shown in Fig. 6, with the mold opened for the demolding of the steering wheel.
  • Fig. 12 is a partly enlarged sectional view of the steering wheel as shown in Fig. 11.
  • Fig. 13 is a graph showing the relationship between the tensile strength of the covering of the steering wheel and the water content in the polyol mixture.
  • Fig. 14 is a graph showing the relationship between the tear strength of the covering of the steering wheel and the water content in the polyol mixture.
  • Fig. 15 is a graph showing the relationship between the thickness of the skin of the steering wheel and the pressure in the cavity.
  • Fig. 16 is a sectional view showing another example of the mold.
  • Fig. 17 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 0.665 kPa (5 Torr).
  • Fig. 18 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 1.596 kPa (12 Torr).
  • Fig. 19 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 1.995 kPa (15 Torr).
  • Fig. 20 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 2.66 kPa (20 Torr).
  • Fig. 21 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 3.99 kPa (30 Torr).
  • Fig. 22 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 6.65 kPa (50 Torr).
  • Fig. 23 is a sectional photomicrograph showing the covering of the steering wheel produced with the pressure in the cavity adjusted to 13.3 kPa (100 Torr).
  • Fig. 24 is a sectional photomicrograph showing the covering of the steering wheel produced in the conventional fleon-based foaming.
  • the process for producing an integral skin polyurethane foam comprises expanding a reacting mixture containing substantially no blowing agent in an evacuated mold cavity.
  • the phrase "containing substantially no blowing agent” means that the reacting mixture is not deliberately incorporated with any blowing agent (including freon, methylene chloride, water, and fine bubbles) for the purpose of blowing or blowing control.
  • the reacting mixture may contain slight amounts of various gases which are originally present therein, slight amounts of air entrapped inevitably thereby during cycling, and slight amounts of moisture absorbed inevitably thereby.
  • the phrase also means that the reacting mixture may contain a variety of blowing agents in such small amounts that they hardly affect the blowing control.
  • the water content (due to the inevitable moisture absorption) in the polyol mixture should preferably be limited to 0.4 wt%. With a water content in excess of 0.4 wt%, the polyol mixture will partly remain unreacted on account of reaction between the water and part of the isocyanate. This results in a polyurethane foam poor in physical properties such as tensile strength and tear strength.
  • the extent to which the mold cavity is evacuated varies depending on the kind and desired expansion ratio of the polyurethane foam to be produced. For the production of steering wheels, it is desirable to evacuate the mold cavity to 6.65 kPa (50 Torr) or below in order to form a skin which should have a soft feel as well as a firm feel.
  • reaction rate of the reacting mixture it is desirable to control the reaction rate of the reacting mixture such that the reacting mixture reaching the vent hole cures to seal the vent hole.
  • a lower reaction rate will result in a large amount of the reacting mixture blowing off from the vent hole.
  • a higher reaction rate will cause molding defects such as short shot, pin-holes, and voids.
  • the reacting mixture Once injected into the mold cavity, the reacting mixture rapidly expands and flows under reduced pressure irrespective of the progress of the urethane-forming reaction. This causes the reacting mixture to reach the vent in a much shorter time than in the conventional process. For the reacting mixture to cure when it has reached the vent hole, it is necessary that the reaction rate of the reacting mixture be much higher than in the conventional process.
  • a means to increase the reaction rate is by increasing the amount of the catalyst or by increasing the temperature of the reacting mixture. (The latter means is possible because no freon is used in the present invention.)
  • the method of the present invention is suitable for producing a polyurethane foam around a core metal previously placed in the mold cavity. It is most suitable for the production of steering wheels, with an integral skin polyurethane foam covering a core metal (at least the ring part thereof) placed in the mold cavity.
  • the apparatus for producing an integral skin polyurethane foam comprises a mold having a cavity and a vent hole, a vacuum chamber communicating with the cavity through the vent, a vacuum pump to evacuate the cavity through the vacuum chamber, and a sight glass attached to the vacuum chamber so as to make the vicinity of the vent hole visible from the outside of the vacuum chamber.
  • the vacuum chamber may be a space of an evacuated box surrounding the mold cavity or a space which is formed, when the mold is closed, by the groove in the periphery of the mold cavity.
  • the reacting mixture is injected into the evacuated mold cavity.
  • the reacting mixture contains substantially no blowing agent, it contains slight amounts of gases originally present therein and absorbed inevitably by it during its cycling. Under reduced pressure, these gases rapidly vaporize, causing the reacting mixture to expand rapidly in a very short time. As the result, the reacting mixture flows in the cavity and fills the cavity. Simultaneously with the expansion, the reacting mixture undergoes the exothermic urethane-forming reaction which brings about curing.
  • the reacting mixture in contact with the inner surface of the mold cavity permits heat to dissipate through the walls of the mold cavity. This heat dissipation makes the urethane-forming reaction slow relative to that at the center and hence prevents the reacting mixture from becoming viscous.
  • the gas bubbles near the inner surface of the mold cavity rupture easily under reduced pressure, and the released gas is removed. Thus there is formed a non-porous solid skin containing even very few minute bubbles.
  • the evacuated cavity helps avoid such defects as pinholes, voids, and short shot. Unlike the conventional foaming by freon, this obviates the necessity of over-packing the reacting mixture to form the skin and to ensure the complete filling and air escape, which leads to the reduction of material loss. In this way, it is possible to produce a superior polyurethane foam composed of a highly expanded core and a solid skin.
  • the foaming due to the expansion of the gases absorbed by the reacting mixture is not by the vaporization of a gas, unlike the foaming by freon; therefore, it does not take away the reaction heat of the reacting mixture after injection. This permits the temperature rise of the reacting mixture and hence reduces the cure time.
  • the water content in the polyol mixture is limited to 0.4 wt%, so as to reduce the amount of the isocyanate to be consumed by water and hence to reduce the amount of the polyol mixture which will otherwise remain unreacted. This contributes to the improved physical properties (such as tensile strength and tear strength) of the resulting polyurethane foam.
  • the mold cavity should preferably be evacuated 6.65 kPa (50 Torr) or below, so as to help the gas bubbles to rupture in the reacting mixture in contact with the inner surface of the mold cavity. This makes the skin thick and eliminates the minute gas bubbles which will otherwise remain in the skin.
  • the reacting mixture is so formulated as to establish a proper reaction rate such that it cures to seal the vent as soon as it reaches the vent.
  • a reaction rate higher than that of the freon-containing reacting mixture. This contributes to improvement in production efficiency.
  • Evacuating the mold cavity offers another advantage in the case where a core metal is placed in the mold cavity. Even though the reacting mixture is subject to turbulence by the core metal, the turbulence under reduced pressure is less liable to cause defects such as pinholes, voids, and short shot. This permits one to select an adequate place for gating more freely and to reduce the number of vents.
  • the combination of an evacuated mold cavity and a core placed therein offers an advantage that an almost non-porous solid adhesive layer is formed on the core, because the core functions as a heat sink such that it absorbs reaction heat from the reacting mixture in contact with it, thereby stopping the reacting mixture from becoming viscous, and the less viscous reacting mixture releases gas from gas bubbles under reduced pressure.
  • the core is that of a steering wheel and at least the ring of the core is placed in the mold cavity.
  • the method of the present invention will prevent defects (such as weld line, pinholes, voids, and short shot) from occurring at the point where the flows of the reacting mixture meet one another.
  • the apparatus for producing an integral skin polyurethane foam has a vacuum chamber communicating with the mold cavity through the vent.
  • This vacuum chamber functions as an accumulator.
  • the vacuum chamber prevents the pressure in the mold cavity from increasing as the reacting mixture expands after injection.
  • the apparatus has a sight glass which makes the vicinity of the vent hole visible from the outside of the vacuum chamber.
  • the sight glass permits one to confirm the blowing off of the reacting mixture from the vent hole and to observe the reacting mixture expand, with the vacuum chamber kept closed.
  • FIG. 1 An embodiment of the present invention in the production of a steering wheel pad will be described with reference to Figs. 1 to 5.
  • This example employs an apparatus which is made up of (a) a split mold 1, (b) a vacuum chamber 11 arranged in the mold 1, (c) a vacuum pump 20 to evacuate the vacuum chamber 11, and (d) an injecting mechanism 21 which is attached to the vacuum chamber 11 and is intended to inject the reacting mixture into the cavity 4 of the mold 1.
  • a split mold 1 a vacuum chamber 11 arranged in the mold 1
  • FIG. 1 to 5 An embodiment of the present invention in the production of a steering wheel pad will be described with reference to Figs. 1 to 5.
  • This example employs an apparatus which is made up of (a) a split mold 1, (b) a vacuum chamber 11 arranged in the mold 1, (c) a vacuum pump 20 to evacuate the vacuum chamber 11, and (d) an injecting mechanism 21 which is attached to the vacuum chamber 11 and is intended to inject the reacting mixture into the cavity 4 of the mold 1.
  • the mold 1 is made up of a stationary half 2 and a movable half 3, which form a cavity 4 when closed.
  • the split molds In the PL (parting line) surface 2a of the stationary half 2 and the PL surface 3a of the movable half 3, the split molds have grooves which form a sprue 6, runner 7, and gate 8 through which the reacting material is injected into the cavity 4.
  • This clearance functions as an air vent land for venting (mentioned later).
  • a vent hole 5 is formed at that position L of the stationary half 2 where the filling of the cavity with the reacting mixture completes.
  • the vent hole 5 is usually 1-10 mm in diameter. With a diameter smaller than 1 mm, the vent hole 5 does not perform venting as desired, with the final filling position of the reacting mixture fluctuating. With a diameter larger than 10 mm, the vent hole 5 leaves a noticeable vent mark which makes the molded article look poor.
  • the vent hole 5 in this example is a straight one, 15 mm long and 3 mm in diameter.
  • the mold 1 may be made of aluminum or electroformed for economy, because it merely needs to withstand a foaming pressure, which is usually 50-500 kPa.
  • the vacuum chamber 11 is made up of an upper casing 12 to which the stationary half 2 is fixed and a lower casing 13 to which the movable half 3 is fixed.
  • the mating surface of the lower casing 13 is provided with a sealing O-ring 14, which makes the closed vacuum chamber 11 airtight.
  • the lower casing 13 is also provided with a suction port 16, which is connected to a vacuum pump 20 through a suction hose 15 and a leak valve 17, as shown in Fig. 5.
  • the vacuum chamber 11 in this example is constructed such that it accommodates the mold 1, forming a space K therein.
  • the injection mechanism 21, as shown in Fig. 5. is made up of a storage tank 25 for the polyol mixture, a storage tank 26 for the isocyanate, a mixing head 22, and two circuits 29, each connecting the storage tank and the head through a high-pressure pump 27 and filters 28.
  • This construction permits the mixing and circulation of the polyol mixture and isocyanate.
  • the mixing head 22 is provided with an injection nozzle 23 which can be connected to the sprue 6 of the mold 1 through O-rings 24.
  • the reacting mixture used in this example is composed of the above-mentioned polyol mixture and isocyanate.
  • the reacting mixture contains substantially no blowing agent deliberately added, with the water contain in the polyol mixture limited to no more than 0.4 wt%.
  • the temperature of the reacting mixture is higher than that of the conventional fleon-containing reacting mixture.
  • the polyol mixture is kept at about 40-50°C and the isocyanate is kept at about 25-30°C in this example, whereas the polyol mixture and isocyanate are both kept at about 25-30°C in the conventional freon-based foaming.
  • the freon-free reacting mixture in this example is more viscous than the conventional fleon-containing one; this disadvantage is eliminated by raising the temperature.
  • the molding apparatus has many parts common to that in the first example. Basically, it is constructed of a mold 1, a vacuum chamber 11, vacuum pump 20, and a injecting mechanism 21. Those parts common to that in the first example are indicated by like reference numbers in Figs. 6 to 11, and their description is not repeated except for the supplementary description that follows.
  • the core 42 of the steering wheel 41 is composed of a boss, a ring, and spokes connecting the boss and ring.
  • the mold 1 is intended to form the covering 43 around the ring and spokes of the core 42.
  • the mold 1 is composed of an upper stationary half 2 and a lower movable half 3. They have grooves 4a, which form a circular cavity 4 when they are closed. At the center of the cross-section of the cavity 4 is placed the core 42 (including the entire ring and a part of the spoke).
  • a gate 8 opens on the outer periphery of the groove 4a (the left side in Fig. 6). Upon injection into the cavity 4 through the gate 8, the reacting mixture M flows in two directions in the cavity 4 and the two flows meet at position L (at the right side in Fig. 6) where the filling of the cavity is completed.
  • a vent hole 5 through which the cavity 4 communicates with the space in the vacuum chamber 11.
  • the lower casing 13 of the vacuum chamber 11 is provided with a sight glass 51 which makes the vicinity of the vent hole 5 visible from the outside of the vacuum chamber 11, as shown in Figs. 9 and 10.
  • the sight glass 51 is made up of an opening 52 formed in the lower casing 13, a transparent plate 54 of glass or plastics which is pressed against the inside of the lower casing 13, with a seal ring 53 placed between them, so as to close the opening 52 from the inside, and a frame 56 which is fastened to the lower casing 13 by bolts 55 such that it presses the periphery of the transparent plate 54. It is desirable to place a gasket 57 between the frame 56 and the transparent plate 54 and between the frame 54 and the lower casing 13.
  • the stationary half 2 and the upper casing 12 are integrally constructed, and the movable half 3 and the lower casing 13 are also integrally constructed.
  • the lower casing 13 is connected to a hydraulic cylinder ram (not shown), so that it is raised and lowered as the mold is closed and opened. At the time of mold closing, the lower casing 13 is raised until its periphery comes into contact with the periphery of the upper casing 12.
  • the reacting mixture used in this example is composed of a polyol mixture and an isocyanate. It contains substantially no blowing agent deliberately added, and the water content in the polyol mixture is limited to less than 0.4 wt%.
  • the temperature of the reacting mixture is set higher than that of the conventional freon-containing reacting mixture.
  • Another advantage in this example is that the covering 43 firmly adheres to the ring of the core 42 owing to the solid adhesive layer 47.
  • the water content in the polyol mixture is limited to less than 0. 4 wt%, as mentioned above.
  • the following experiment was carried out.
  • Three reacting mixtures containing no freon were prepared according to the formulation shown in Table 1, with the water content in the polyol mixture limited to 0.13 wt%, 0.35 wt%, and 0.54 wt%.
  • Each of the reacting mixtures was made into the covering of the steering wheel under the molding conditions shown in Table 2. The covering was tested for physical properties.
  • a reacting mixture containing freon was prepared according to the formulation shown in Table 1, with the water content in the polyol mixture limited to 0.22 wt%.
  • the reacting mixture was made into the covering of the steering wheel under the conventional molding conditions shown in Table 2.
  • the covering was tested for physical properties.
  • the covering of the steering wheel produced as mentioned above was tested for tensile strength and tear strength at room temperature using a test piece cut out of the highly expanded core part. The results of the test are shown in Fig. 13 (tensile strength) and Fig. 14 (tear strength). It is noted that the polyurethane foam in this example is superior in tensile strength and tear strength to the conventional freon-based one, even in the case where the water content in the polyol mixture is 0.54 wt%. It is also noted that a pronounced effect is obtained when the water content in the polyol mixture is lower than 0.4 wt%.
  • Example 2 In order to see how the pressure in the cavity affects the thickness of the skin in Example 2, a reacting mixture containing no freon was prepared according to the formulation shown in Table 1, with the water content in the polyol mixture limited to 0.35 wt%, and the reacting mixture was made into the covering of the steering wheel under the molding conditions shown in Table 2, with the pressure in the cavity adjusted to 0.665, 1.596, 1.995, 2.660, 3.990, 6.650 and 13.3 kPa (5, 12, 15, 20, 30, 50, and 100 Torr). The covering was tested for the thickness of the skin. The results are shown in Fig. 15. It is noted that the thickness of the skin steeply increases when the pressure in the cavity is 6.65 kPa (50 Torr) or below.
  • the sectional photomicrographs showing the covering of the steering wheel produced in this experiment are shown in Figs. 17 to 23.
  • the covering of the steering wheel shown in Figs. 17 to 23 was produced with the pressure in the cavity adjusted respectively to 0.665, 1.596, 1.995, 2.660, 3.990, 6.650 and 13.3 kPa (5, 12, 15, 20, 30, 50, and 100 Torr).
  • the sectional photomicrograph, showing the covering of the steering wheel produced in the conventional fleon-based foaming under the conventional molding conditions shown in Tables 1 and 2 is shown in Fig. 24.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Environmental Sciences (AREA)
  • Toxicology (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Molding Of Porous Articles (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Claims (6)

  1. Procédé de production d'une mousse en polyuréthanne à peau intégrée dans une cavité de moule qui comprend :
    (1) la mise de la cavité du moule sous vide pour réduire sa pression jusqu'à une pression barométrique prédéfinie;
    (2) l'injection, dans la cavité du moule où le vide a été fait, d'un mélange réactionnel, formant des uréthannes, contenant un mélange de polyols et ne contenant pratiquement pas d'agent moussant de petites quantités de gaz étant présentes à l'origine dans ledit mélange réactionnel et étant absorbées inévitablement par lui pendant son pompage; et
    (3) l'abandon du mélange réactionnel formant des uréthannes pour qu'il réagisse et s'expanse par suite de l'expansion desdits gaz absorbés par ledit mélange réactionnel, dans la cavité du moule où le vide a été fait, pour formation de la mousse de polyuréthanne à peau intégrée.
  2. Procédé pour la production d'une mousse de polyuréthanne à peau intégrée telle que définie dans la revendication 1, dans lequel le vide est fait dans la cavité du moule jusqu'à 6,65 kPa (50 torr) ou au-dessous.
  3. Procédé pour la production d'une mousse de polyuréthanne à peau intégrée telle que définie dans la revendication 1, dans lequel le mélange réactionnel a une vitesse de réaction contrôlée de telle façon que, quand le mélange réactionnel injecté atteint un orifice d'évent du moule, la partie du mélange réactionnel qui est en contact avec ledit orifice d'évent durcit pour fermer ledit orifice d'évent.
  4. Procédé pour la production d'une mousse de polyuréthanne à peau intégrée telle que définie dans la revendication 1, dans lequel une préforme métallique est préalablement placée dans la cavité du moule.
  5. Procédé pour la production d'une mousse de polyuréthanne à peau intégrée telle que définie dans la revendication 4, dans lequel ladite préforme métallique est celle d'un volant composé d'un moyeu, d'une jante et de rayons reliant le moyeu et la jante et dans lequel au moins la jante de la préforme métallique est placée dans la cavité du moule.
  6. Procédé tel que défini dans la revendication 1, dans lequel ledit mélange de polyols contient moins de 0.4 % d'eau en masse.
EP92116164A 1991-09-26 1992-09-22 Méthode pour la production d'un produit moulé de mousse de polyuréthane à peau intégrale Expired - Lifetime EP0534358B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP277285/91 1991-09-26
JP3277285A JP2518481B2 (ja) 1991-09-26 1991-09-26 自己スキン層付きポリウレタンフォ―ムの製造方法及び製造装置

Publications (2)

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EP0534358A1 EP0534358A1 (fr) 1993-03-31
EP0534358B1 true EP0534358B1 (fr) 1996-12-04

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Also Published As

Publication number Publication date
DE69215628D1 (de) 1997-01-16
EP0534358A1 (fr) 1993-03-31
US5449698A (en) 1995-09-12
JPH0671769A (ja) 1994-03-15
JP2518481B2 (ja) 1996-07-24
DE69215628T2 (de) 1997-04-24

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